This invention relates to fluid pumps and particularly to fluid pumps having reciprocating cylinders driven by electro-magnetic coils.
The primary advantage of such pumps is that the pistons are driven by electro-magnetic coils which surround the pistons, thereby eliminating the need for electrical motors or other driving means. Such pumps usually include a magnetic piston which is surrounded by a single elongated electronic coil. Actuation of the coil causes reciprocation of the piston.
Usually only a single coil is utilized which surrounds the piston. Some pumps have utilized two separate coils located at opposite ends of the pistons's reciprocating path. Both of these arrangements are disadvantageous inasmuch as they do not concentrate the maximum electrical power on the piston during all positions of the piston. Consequently there are spots where the force acting on the piston is weakened and therefore the force is not constant throughout the cycle of the piston.
Another disadvantage of present devices arises from the fact that the coil acts directly upon the piston which is utilized for forcing the fluid through the pump. This arrangement limits the flexibility of the design inasmuch as the size of the piston must be chosen not only to accomplish the proper pumping force, but also to respond properly to the electromagnetic forces emitted by the coil. Thus, in present devices it is difficult to vary the size of the piston without upsetting the delicate balance between the force exerted by the coil and the counteracting force exerted by the fluid within the pump.